This invention relates in general to apparatus for automatically injecting mature animals, especially birds, with a vaccine or other fluid substance. More particularly, the invention relates to an improved retention device for insuring proper positioning of the animal relative to the hypodermic needle of the apparatus while preventing premature actuation of the apparatus.
Automatic animal vaccinating devices are well known in the prior art. Typical examples of such devices are disclosed in U.S. Pat. Nos. 4,108,176 (Walden), 3,641,998 (Lyon et al.), 3,964,481 (Gourlandt et al.) and in U.S. Application Ser. No. 881,033, which is pending and has a common assignee with this application. The present invention is compatible for use with either of the systems disclosed in the latter two cases and, therefore, the contents of those cases are hereby incorporated by reference. Typically, the prior art devices function by the operator placing the animal alongside a positioning fixture and then actuating a switch, either manually or by forcing a portion of the animal's body against an actuator adjacent the positioning fixture. Generally, the positioning fixture accommodates various orientations of the animal's body to permit either subcutaneous or intramuscular vaccination.
Presently existing devices are suitable for use with very young animals, for example, with baby chicks which generally are inoculated within a few days of birth. Such animals are easy to manipulate into position and do not offer significant resistance to the operator. Also, in the specific case of baby chicks, the layer of feathers or down which covers the chick's body is relatively thin and closely conforms to the underlying tissue. Therefore, when the chick's body is pressed against the switch actuator with sufficient force to activate the syringe drive mechanism and to inject the hypodermic needle into the body, the needle will be injected into the muscle or skin of the bird and not merely into the feathers. The docile nature and small size of the bird also minimize any shifting of the bird during the injection process.
However, in the case of more mature birds, such as adult chickens or turkeys, the animal generally is much more active during the vaccination process and is not apt to remain still, but will fight the operator vigorously. In such a case, movements of the bird may cause the animal to be withdrawn from the location at which the needle protrudes, before the needle has effectively been injected into the skin or muscle and the fluid has been transferred. Also, in the case of a mature bird, the layer of feathers covering the skin is generally thicker and stiffer than in the case of the chick. This layer of feathers may offer sufficient resistance to actuate the switch and start the injection process before the underlying layer of skin is sufficiently close to the needle to insure effective penetration of the needle into the skin. In other words, there is the possibility that the needle will only penetrate the outer layer of feathers and not the underlying layer of skin, and that the fluid may be injected only into this feather layer, thereby invalidating the vaccination. Not only is this condition wasteful and, therefore, needlessly costly, but also the operator cannot be positive that the bird has been vaccinated properly.
The extended position of the outward end of the needle also must be essentially the same at each injection, to insure both effectiveness of the vaccination and the safety of the animal.
Therefore, it is an object of the present invention to position a violently struggling animal properly with respect to the vaccinating syringe to insure effective injection of the animal.
It is a further object of the present invention to insure that the automatic vaccination apparatus is actuated only when the portion of the animal's body to be injected is in sufficient proximity to the hypodermic needle to guarantee proper penetration of the needle into the animal and, thus, to prevent premature activation of the vaccination apparatus.
It is a still further object of the present invention to permit injection of the hypodermic needle into the animal at a wide range of angular inclinations without requiring modification or repositioning of the placement fixture.
It is a still further object of the present invention to insure repeatability of the amount of protrusion of the hypodermic needle beyond the retention plate, available for injection into the animal.